1. Field of the Invention
The present invention relates to a novel crystalline naphthalene-1,5-disulfonic acid salt of a substituted pyrrolidine compound that is useful for treating pulmonary disorders. This invention also relates to pharmaceutical compositions comprising the crystalline compound or prepared from the crystalline compound, processes and intermediates for preparing the crystalline compound and methods of using the crystalline compound to treat a pulmonary disorder.
2. State of the Art
Commonly-assigned U.S. Patent Publication No. 2004/0254219 to Mathai et al., discloses novel substituted pyrrolidine compounds that are useful for treating pulmonary disorders, such as chronic obstructive pulmonary disease (COPD) and asthma. In particular, the compound, 2-[(S)-1-(8-methylaminooctyl)pyrrolidin-3-yl]-2,2-diphenylacetamide is specifically disclosed in this application as possessing muscarinic antagonist activity.
The chemical structure of 2-[(S)-1-(8-methylaminooctyl)pyrrolidin-3-yl]-2,2-diphenylacetamide is represented by formula I:

Therapeutic agents useful for treating pulmonary disorders are advantageously administered directly into the respiratory tract by inhalation. In this regard, several types of pharmaceutical inhalation devices have been developed for administering therapeutic agents by inhalation including dry powder inhalers (DPI), metered-dose inhalers (MDI) and nebulizer inhalers. When preparing pharmaceutical compositions and formulations for use in such devices, it is highly desirable to have a crystalline form of a pharmaceutically acceptable salt the active agent that is neither hygroscopic nor deliquescent and which has a relatively high melting point (i.e. greater than about 150° C.) thereby allowing the material to be micronized without significant decomposition.
No salt forms of the compound of formula I, 2-[(S)-1-(8-methylaminooctyl)pyrrolidin-3-yl]-2,2-diphenylacetamide, have been reported previously. Accordingly, a need exists for a stable, non-deliquescent salt form of the compound of formula I which has an acceptable level of hygroscopicity and a relatively high melting point.